1. Field of the Invention
The present invention relates to a planar source apparatus and a liquid display apparatus, further in details, relates to an improvement in a planar light source apparatus for diffusing light of a point light source provided along a hollow region formed on a rear face side of a diffusing plate at inside of the hollow region and irradiating the diffused light to a rear face of a liquid crystal panel or the like.
2. Description of the Related Art
There are a side light of type and an immediate downward type of planar light source apparatus for irradiating a display screen from a rear face thereof by irradiating light to a rear face of a liquid crystal panel. According to a planar light source apparatus of a side light type (also refers to as edge light type), a light source is arranged at a side face of a cabinet, and according to a planar light source of an immediate downward type, a light source is arranged on a rear face of a cabinet to be opposed to a liquid crystal panel. Further, there is a planar light source apparatus of a side light type using a light guide plate for guiding light from a light source to an opening portion of a cabinet. According to a planar light source apparatus using a light guide plate, light emitted from a side light portion comprising a line light source of a cold cathode fluorescent lamp (CCFL), a light emitting diode (LED) or the like is reflected at inside of a light guide plate and diffused by a diffusing pattern provided at inside of the light guide plate to thereby take out light planarly from an opening portion.
Generally, according to a planar light source apparatus using a point light source of LED or the like as a light emitting element, when a brightness of a display screen is intended to increase, it is conceivable to increase a density of a number of elements by increasing a number of light emitting elements, or increasing current supplied to respective point light sources. However, in either of the cases, a temperature of a surrounding portion of the point light source is elevated by heat generated from each point light source in accordance with emission of light.
Hence, there is proposed a planar light source apparatus provided with heat radiating means at a board attached with a point light source (for example, Patent References 1 and 2). According to the planar light source apparatus, heat radiating performance can be promoted and therefore, a density of a number of elements of point light sources and current supplied to respective point light sources can be increased. However, in such a planar light source apparatus of a prior art, a light guide plate is used and therefore, there poses a problem that light-weighted formation and thin-size formation of the planar light source apparatus are not facilitated.
Generally, a wiring pattern provided on a board for supplying power to respective point light sources is constituted by combining series connection and parallel connection since when electricity feed lines to point light sources are constituted only by series connection, a voltage applied to a light source unit becomes high. Therefore, when a number of elements of the point light sources is increased, the wiring pattern on the board is complicated, an area of the board is increased and therefore, there also poses a problem that a side light portion is large-sized.
[Patent Reference 1] JP-A-2002-229022
[Patent Reference 2] JP-A-2003-76287
As described above, according to the planar light source apparatus of the prior art, the light guide plate is used and therefore, there poses a problem that light-weighted formation and thin-size formation of the apparatus are not facilitated. Further, when the number of elements of the point light sources is increased, the wiring pattern on the board is complicated, the area of the board is increased and therefore, there poses a problem that the side light portion is large-sized.